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\title{A Survey On Near Field Communication}


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\author{\IEEEauthorblockN{Wen Shen and Issak Gezehei }
\IEEEauthorblockA{Computing and Information Science\\
Masdar Institute of Science and Technology\\
PO Box 54224, Abu Dhabi, UAE\\
Email: \{wshen,igezehei\}@masdar.ac.ae}
}


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\begin{abstract}
Near Field Communication (NFC) is a short-range high frequency wireless communication technology which enables the exchange of data between devices in close proximity. Two modes of communication are involved in the communication process of NFC-enabled devices: active mode and passive mode. In active mode, both the intiator and the target device generate an Radio Frequency signal on which the data is carried. In passive mode, only the initiator generates an RF field. In this work, we will present a detailed survey on the principles, the application, the challenges and the trends on Near Field Communication.
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\section{Introduction}
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Near Field Communication (NFC) is a short-range high frequency wireless communication technology which enables the exchange of data between devices over close proximity up to about 20 centimeters\cite{kerschbergernear}. The techonology behind NFC is an extension of the existing radio-frequency identification(RFID) standards including ISO/IEC 14443 proximity-card standard and FeliCa standard. NFC is generally compatible with existing RFID systems, but its architecture is different in principle. RFID has only a reader-tag structure while an NFC device can be both reader and transmitter. 

In 2002, NFC was jointly developed by NXP Semiconductors and Sony. In 2003, NFC was approved as an ISO/IEC standard and later as an European Computer Manufacturers Association (ECMA) standard. In 2004, for better standardization the NFC Forum was founded by Nokia, NXP Semiconductors and Sony, and now has 160 memebers. The NFC Forum promotes NFC by developing specifications, ensuring interoperability among devices and services, and educating the market about NFC technology\cite{nfcforum2012}.

NFC has a wide application in many areas of life. Current and potential applications include contactless transactions, data exchange, simplified setup of more complex communications such as Wi-Fi and documents identification. Communication is also possible between an NFC device and an unpowered NFC chip-tag.

In this paper, we will present a detailed survey on the principles and application of NFC as well as the challenges in this area.
\section{Principles of Near Field Communication}
NFC is a new, very short range, wireless point-to-point interconnection technology, evolved from a combination of earlier RFID contactless identification and interconnection technologies. It enables users of handsets to access content and services in an intuitive way by simply \textquotedblleft touching" smart objects, that is connecting devices just by holding them next to each other. The communication is based on inductive coupling. The 13.56 MHz carrier frequency is used and the maximum data rate is 424 kbps\cite{strommer2006application}.
\subsection{Modes of Communication}

There are two modes of communication-active mode and passive mode, which are defined by NFC protocols.  In these modes of communication, two types of NFC devices are involved. These are known as the Initiator and Target of the communication. The Initiator is the device that initiates the communication and it controls the data exchanges. The Target device is the one that responds to the requests from the Initiator.
\subsubsection{Active Mode of Communication}
In the active NFC mode of communication, both devices generate an RF signal on which the data is carried\cite{ecma2006near}(i.e., In this mode, both Initiator and Target device communicate by alternately generating their own field,  device deactivates its RF field while it is waiting for data, both devices typically need to have a power supply).


\subsubsection{Passive Mode of Communication}
In this mode of communication, only one NFC device generates an RF field. The second passive device which is the target uses a technique called load modulation to transfer the data back to the primary device or initiator\cite{ecma2006near} (i.e., the Initiator device provides a carrier field and the target device answers by modulating existing field, the Target device may draw its operating power from the Initiator-provided electromagnetic field, thus making the Target device a transponder).

The communication is terminated either on the command from the application or when devices move 
out of range.
\begin{figure}[ht!]
      \includegraphics{app.png}
  \caption{Overview of the NFC-Forum operation modes\cite{kerschbergernear}}
\end{figure}
\subsection{Operation Modes}

In addition to the NFC modes of communication, three operation modes are also defined: reader/writer mode, peer-to-peer mode, and card emulation mode\cite{nfcforum2012faq}. The different operating modes are based on two NFC standards: Near Field Communication Interface and Protocol(NFCIP-1) and Near Field Communication Interface and Protocol-2(NFCIP-2).

NFCIP-1 combines the following two RFID communication protocols: MIFARE(ISO/IEC 14443 Type A) and FeliCa(JIS X 6319-4), and extends them with new communication possibilities and a new transport protocol. NFCIP-2 combines NFC with the functionality of RFID readers. In this way, NFC is compatible with most RFID devices\cite{weidar2011}.

RFID has strictly one or more passive components(tags) and one active component(reader).  However, for NFC devices it is possible to communicate with each other, acting as tag or as reader/writer. To ensure this, the NFC-Forum defines the following operation modes: \textit{peer to peer mode, reader/writer mode and card emulation mode}.  An outline is given in Figure 1.

While most RFID readers are designed to be the only active devices in range, for NFC devices this assumption is not possible, therefore a collision avoidance is used. The recognition speed of devices in range should also stay beyond 200ms for proper usability. Many NFC devices are mobile and therefore have a limited power capacity, since higher recognition speed requires more energy. There will be always a compromise between the detection speed and the energy consumption.

\subsubsection{Peer to Peer Mode}
\begin{figure}[ht!]
      \includegraphics{model.png}
  \caption{NFC Peer to Peer Protocol Stack versus OSI Reference Model\cite{nfclink11}}
\end{figure}
\textit{Peer to Peer Mode} enables communication between two NFC devices: Initiator and Traget.

The \textit{Peer to Peer Mode} protocol stack is organized similar to the \textit{OSI Reference Model}, but has only 4 layers: Physical, Media Access Control(MAC), Logical Link Control(LLC) and Application. The Physical and MAC layer are specified by NFCIP-1 and the LLC is specified by the NFC Forum-Logical Link Control Protocol(LLCP)-Technical Specification.

The NFC interface can operate in two different modes: active and passive. An active device generates its own radio frequency(RF) field, while a passive device has to use inductive coupling to transmit data. In the active communication mode, both the Initiator and the Target use their own RF field to enable communication. The Initiator starts the NFCIP-1 communication. The Target responds to an Initiator command in the active communication mode using self-generated modulation of self-generated RF field. In the passive communication mode, the Initiator generates the RF field and starts the communication. The Target responds to an Initiator command in the passive communication mode using a load modulation scheme. The main difference in these modes is the energy consumption of Initiator and Target. In the active communication mode the power required for generating the RF field is shared by Initiator and Target, while in passive communication mode the Initiator has to supply the power required for the field generation\cite{nfclink11}.

To ensure proper communication, NFCIP-1 defines the following protocol flow: All devices should stay in Target mode and do not genereate an RF field as default. A device switches only to Initiator mode if it is required by the application, and the application defines the use of active or passive communication mode. Before activating the RF field the Initiator has to check against another active sender so no other communication is disturbed. If no other RF field is detected the Initiator starts communication and tells the Target to use active or passive communication mode and transmission speed. After communicaiton, both devices switch back to Target mode and deactivate their RF fields.

In the MAC layer only the Initiaor can start a data transmission, the LLCP enables Asynchronous Balanced Mode(ABM) where additionally the Target is able to start a data tansfer and error recovery is possible. LLCP is also capable of managing multiple application's access at the same time by multiplexing. It delivers a Connectionless Transport Protocol with a minimum of protocol overhead, for use when a higher level protocol uses flow control mechanisms. A connection-oriented transport protocol is also provided, which ensures a guaranteed and sequenced delivery of the data units. LCCP does not provide a secure data transfer mode.

\subsubsection{Reader/Writer Mode}
\textit{Reader/Writer Mode} allows the NFC devices to communicate with NFC Forum Tags. These tags are typically passive components. Thus, this mode is also known as \textit{Passive Mode}.

The tags can be placed in posters or other places and by touching the tag with the NFC device, the stored information is transmitted to the device. They can contain only information or perform actions on the device.

This mode is fully compatible with the ISO/IEC 14443 and FeliCa technology and because of this, NFC devices can be used as readers/writers in existing RFID infrastructures. 
\subsubsection{Card Emulation Mode}
The optional \textit{Card Emulation Mode} allows the NFC device to communicate with well known RFID readers. The device therefore can emulate one or more RFID smartcards. With this mode it is possible to use the existing contactless infrastructure, e.g., for payment or admission control.

The emulation of the smartcard can be done either in application or in a so called \textit{Secure Element}. A \textit{Secure Element} is a device, similar to a real smartcard but uses an interface to the NFC device to transfer its data.

In combination with the \textit{Reader/Writer Mode}, it is possible to implement a mode similar to the \textit{Peer to Peer Mode}, but it is simpler because the protocol stack defined in \textit{Peer to Peer Mode} is not needed. With the correct hardware implementation it is possible to use this mode even when the NFC device is switched off or is short of energy.
\subsection{NFC Modulation and RF Signal}
In order to ensure reliable communications while not consuming too much power, the RF signal format and modulation for NFC systems has been developed. The NFC modulation format has also been chosen to meet the requirements of both active and passive modes of operation.

NFC uses an unlicensed radio frequency ISM(short for \textquotedblleft industrial, scientific and medical") band-the global 13.56 MHz allocation. Amplitude shift keying (ASK) is also used as the format for the NFC modulation. Most of the RF energy is concentrated in the allowed 14 kHz bandwidth, althrough the sidebans may extend out as far as $\pm$ 1.8 MHz.

NFC employs two different coding systems on the RF signal to transfer data. In most cases a level of 10\% modulation is used, with a Manchester coding formatt. However for an active device transmitting data at 106 kbps, a modified Miller coding scheme is used with 100\% modulation. In all other cases Manchester coding is used with a modulation ratio of 10\%.

\begin{table}[ht]
\begin{center}
\begin{tabularx}{0.45\textwidth}{ |X|X|X|}
  \hline
  DATA RATE Kbps & ACTIVE DEVICE & PASSIVE DEVICE \\
  \hline
  106 &Modified Miller, 100\%, ASK  & Manchester, 10\%, ASK \\
  \hline
  212 & Manchester, 10\%, ASK &Manchester, 10\%, ASK\\
  \hline
  424 &Manchester, 10\%, ASK & Manchester, 10\%, ASK\\
  \hline
\end{tabularx}
\end{center}
\caption{Coding Scheme for different type of devices at different transfer rates}
\end{table}

\subsubsection{Manchester Coding}
Manchester coding is used for the majorith of cases for the NFC communications. The Manchester coding utilizes the two different transitions that may occur at the midpooint of a period. A low-to-high transition represents a 0 bit, whereas a high-to-low transition stands for a 1 bit\cite{kumar2011near}.

To achieve these conditions it is sometimes necessary to have a transition at the middle of a bit period. Transitions at the beginning of period are disregarded.
\subsubsection{Modified Miller Coding}
The modifier Miller code is a little less intuitive, but provides an efficient form of coding. It is characterised by the pauses occurring in the carrier at different positions of a period. Depending on the information to be transmitted, bits are coded as shown below. A high or \textquotedblleft 1" always encoded in the same way, but a low or \textquotedblleft 0" is encoded differently dependent upon what preceded it\cite{kumar2011near}.
\subsection{NFC Tags and Tag Types}
One of the key elements of NFC, near field communications technology is the ability for NFC enabled devices to be able to be touched onto passive \textquotedblleft NFC tags." This facility of NFC technology is a key enabler for many applications.

NFC tags are passive devices that can be used to communicate with active NFC devices (an active NFC reader/writer). The NFC tags can be used within applications such as posters, and other areas where small amounts of data can be stored and transferred to active NFC devices. Within the poster the live area can be used as a touch point for the active NFC device.
The stored data on the NFC tag may contain any form of data, but common applications are for storing URLs from where the NFC device may find further information. In view of this only small amounts of data may be required. NFC tags may also be used.

In order that the communication between the active NFC reader/writer and the passive NFC tag was defined. The NFC forum introduced their first standardised technology architecture and standards for NFC compliant devices in June 2006. This included the NFC Data Exchange Format, NDEF, and three Record Type Definitions, RTD. These are for smart poster, text, and Internet resource reading applications.

There are four basic tag types that have been defined. These are given designations 1 to 4 and each has a different format and capacity. These NFC tag type formats are based on ISO 14443 Types A and B which is the international standard for contact-less smartcards) and Sony FeliCa which conforms to ISO 18092, the passive communication mode, standard).

The advantage of keeping the NFC tags as simple as possible is that they may be deemed to be disposable in many instances, often embedded in posters that may only have a short life, etc.

The different NFC tag type definitions are as follows\cite{kumar2011near}:
\begin{itemize}
  \item \textbf{Tag 1 Type}  The Tag 1 Type is based on the ISO14443A standard. These NFC tags are read and re-write capable and users can configure the tag to become read-only. Memory availability is 96 bytes which is more than sufficient to store a website URL or other small amount of data. However the memory size is expandable up to 2 kbyte. The communication speed of this NFC tag is 106 kbit/s. As a result of its simplicity this tag type is cost effective and ideal for many NFC applications.
  \item \textbf{Tag 2 Type}   The NFC Tag 2 Type is also based on ISO14443A. These NFC tags are read and re-write capable and users can configure the tag to become read-only. The basic memory size of this tag type is only 48 bytes although this can be expanded to 2 kbyte. Again the communication speed is 106 kbit/s.
  \item \textbf{Tag 3 Type}  The NFC Tag 3 Type is based on the Sony FeliCa system. It currently has a 2 kbyte memory capacity and the data communications speed is 212 kbit/s. Accordingly this NFC tag type is more applicable for more complex applications, although there is a higher cost per tag.
  \item \textbf{Tag 4 Type}   The NFC Tag 4 Type is defined to be compatible with ISO14443A and B standards. These NFC tags are pre-configured at manufacture and they can be either read / re-writable, or read-only. The memory capacity can be up to 32 kbytes and the communication speed is between 106 kbit/s and 424 kbit/s.
  \end{itemize}


From the definitions of the different NFC tag types, it can be seen that type 1 and 2 tags are very different to type 3 and 4 tags, having different memory capacity and makeup. Accordingly it is expected that there is likely to be very little overlap in their applications. Type 1 and type 2 tags are dual state and may be either read/write or read-only. Type 3 and Type 4 tags are read-only, data being entered at manufacture or using a special tag writer.
\subsection{Hardware Architecture}
NFC is an inductive coupled technology, the frequency of the RF field is 13.56 MHz. The specified data rates(106kbs, 212kbs and 424kbs) are a consequence of the compatibility with the ISO/IEC 14443 Type A and FeliCa RFID standards\cite{kumar2011near}.
The main components of the NFC environments are:
\begin{itemize}
  \item \textit{Host-Controller} Application Execution Environment(AEE), the environment where the application rests e.g. mobile phone.
  \item \textit{Secure Element} Trusted Execution Environment(TEE), the secure environment where e.g. credit card data are stored.
  \item \textit{NFC-Controller} Contactless Front-end(CLF), the link between Host and NFC, with an interface to the \textit{Secure Element}.
  \item \textit{NFC-Antenna}
\end{itemize}
\subsubsection{NFC-Controller}
The \textit{NFC-Controller} is the link between \textit{Air Intreface, Host-Controller} and \textit{Secure Element}. The \textit{Host-Controller} is probably a mobile device such as a mobile phone or a smart card key. Between \textit{Host-Controller} and \textit{NFC-Controller} there are interfaces like Serial Peripheral Interface, Inter-Integrated Circuit and Universial Serial Bus in use. For the communication with the \textit{Secure Element} there are typically smartcard interfaces: the NFC wired interface or the single wire protocol in use. The controller works as modulator/demodulator between the analog \textit{Air Interface} and other digital interfaces. The \textit{NFC-Controllers} have integrated micro-controllers, which implement the low level services, so the exchange with the \textit{Host-Controller} is limited to the applicaton Data and some control commands.
\subsubsection{Secure Element}
On most mobile devices there is no way to store secure data directly. But for most NFC application, such a storage system is essential. For such data, the storage needs to be secured from manipulation. Thus, it must be able to execute cryptographic functions and to implement a secure environment to execute security-relevant software. There are several methods to implement the \textit{Secure Element}:
\begin{itemize}
  \item \textit{Software without secure hardware} Software is the most flexible and independent solution, but software could not be optimally secured without the hardware as there is always the possbility that the unsecured hardware is manipulated.
  \item \textit{Device integrated hardware} This is the most host dependent, but most reliable solution. The \textit{Secure Element} is either a part of the host or is built in as its own chip. However, if the user changes the device, the provider of the secure service has to remove the data from the old device and to put it on the new one.
  \item \textit{Changeable hardware} This is a compromise between reliability, usability and costs. Since a hardware interface is needed to plug in the removable \textit{Secure Element}, the production costs of the host device are higher. Such removable devices could be a Secure Memory Card, which combines the secure smartcard funcions with a usual memory card function, or a Universal Integrated Circuit Card.
\end{itemize}

\section{The Application of NFC}
Near Field Communication has evolved from a combination of contactless identification and interconnection technologies including RFID. It allows connectivity to be achieved conveniently over distances of a few centimetres. Two NFC-enabled mobile devices are able to communicate by simply bring them closs together and this greatly simplifies the issues of identification and security, making it far easier to exchange information. In this way it is anticipated that NFC technology will avoid the complex set-up procedures required by some longer range technologies such as Wi-Fi and Bluetooth. Because of these benefits, various applications based on the NFC technology has been developed and are still being developing, e.g., contactless payment solution, health care, Bluetooth and WiFi connections and social networking. In this section, we will focus on some of them.
\subsection{Contactless Payment}
Unlike many other wireless technologies, NFC has a very short range, which makes it a good choice for secure transactions, such as contactless credit card payments. For example, MasterCard and Visa are both members of the NFC Forum, and both companies have been involved in pilot programs that use NFC-enabled phones as a flash payment option. Phones could \textquotedblleft tap and go” using infrastructure already in place for credit card systems such as MasterCard’s PayPass program or Visa’s payWave. Google Wallet allows consumers to store crredit card and store loyalty card information in a virtual wallet and then use an NFC-enabled device at terminals that also accept MasterCard PayPass transactions. Germany, Austria and Latvia have trialled NFC ticketing systems for public trnsport. And China is using it all over the country in public bus transport.
\subsection{Health Care}
In healthcare, everything has to be documented exactly, which is not an easy task. However, NFC technology can help medical professionals identify the information about what treatments a patient should receive as well as track when nurses and doctors have checked in with that patient. 

In the usual medication scheme, a nurse has to find out which medication is required, fetch it, check if its the right, give it to the patient and document it. By the use of an NFC enabled system in the hospital, the personnel could get a medication list, for all of their patients on their mobile devices, and at the pharmacy an automated medication dispenser could provide the correct medications. In the next step the nurse gives the medication to the patients, checking each first by touching the patients ID, it would show which medication is required. Touching next the medication would perform the check and give an alarm if there is anything wrong. If its the right medicine in the right dosage, it will document that it has been given to the patient. Such a system would decrease the problems of medication errors, this would save money and time, and increase the patient’s safety\cite{strommer2006application}.
\subsection{Social Networking}
NFC can be used in social networking situations, such as sharing contacts, photos, videos or files and entering multiplayer mobile games.
Researchers in Technical University of Munich developed an application called NFriendConnector which enables Facebook users to instantaneously initiate and establish Facebook connections using their mobile phones without having to incur any additional search cost. It  allows people who met in a physical space to exchange profile data through their NFC-enabled phones. Their respective statuses would automatically be updated(e.g., I just met Jim and Kate) and they could choose to include their location(e.g., I just met Jim and Kate at this bar).
\subsection{Initiating Bluetooth and WiFi Connections }
It will be slow and inefficient to transfer large amount of information using NFC. However, it will be convenient to use NFC to initiate the connections of other communication protocols such as Bluetooth and WiFi, e.g., two NFC-enabled computers can exchange the parameters of Bluetooth or WiFi communication and establish a secret key by putting two devices toghter in the proximity range to start a NFC connection, then the computers can be put away from each other but the Bluetooth or WiFi communication continues using the session that was established previously.
\section{Comparison between NFC and Existing Communication Technologies}
NFC outperforms serveral existing wireless communication technologies in terms of  \cite{sidanacloud}:
\begin{itemize}
\item setup time required for activation, 
\item usability:  as it is easy to learn and there is minimal interaction with display and keypad,
\item ways it can be used and the consumer experience of using NFC.
\end{itemize}
In this section we will compare NFC with Bluetooth and Wi-Fi. NFC has the following strengths:\cite{nfcforum2012}

\textit{Intuitive}: NFC devices can interact with each other even without a simple touch.

\textit{Versatile}: NFC is ideally applicable to broad areas of applications.

\textit{Open and standards-based}: The underlying layers of NFC technology follow universally implemented ISO, ECMA, and ETSI standards.

\textit{Technology-enabling}: NFC facilitates fast and simple setup of wireless technologies, such as Bluetooth, Wi-Fi.

\textit{Inherently secure}: NFC transmissions are short range (from a touch to a few centimeters).

\textit{Interoperable}: NFC works with existing contactless card technologies

\textit{Security-ready}: NFC has built-in capabilities to support secure applications
\begin{table}[ht]
\begin{center}

 
\begin{tabular}{ | l | l | l |l | l| }
\hline
&&&\\
   & \raisebox{1.5ex} {\textbf{NFC}} & \raisebox{1.5ex} {\textbf{Bluetooth}} &  \raisebox{1.5ex} {\textbf{WiFi}} \\
 
  \hline
    \textbf{Network} &&&\\
  \textbf{Type} & \raisebox{1.5ex} {Point-Point} & \raisebox{1.5ex} {Point-multiple} &\raisebox{1.5ex} { Point-hub}\\
  \hline
  &&&\\
  \raisebox{1.5ex} {\textbf{Range}} & \raisebox{1.5ex} {0.1 m} & \raisebox{1.5ex} {10 m} & \raisebox{1.5ex} {50-100 m}\\
  \hline
 &&&\\
  \raisebox{1.5ex} {\textbf{Speed}}&\raisebox{1.5ex} {424kbps}&\raisebox{1.5ex} {721 kbps}& \raisebox{1.5ex} {11 \& 54 Mbps}\\
  \hline
  &&&\\
   \raisebox{1.5ex} {\textbf{Set-up-time}}& \raisebox{1.5ex} {0.1 s}& \raisebox{1.5ex} {6 s} & \raisebox{1.5ex} {3-5 s}\\
  \hline
  & Active-active&&\\
   \raisebox{1.5ex} {\textbf{Modes}} &  Active-Passive &  \raisebox{1.5ex} {Active-Active} & \raisebox{1.5ex} {Active-Active}\\
  
  \hline
  &&&\\
  \raisebox{1.5ex} {\textbf{Cost}} & \raisebox{1.5ex} {Low} & \raisebox{1.5ex} {Moderate}& \raisebox{1.5ex} {Moderate}\\
  \hline

 \textbf{ Power}&&&\\
  \textbf{Consumtion} & \raisebox{1.5ex} {Low} & \raisebox{1.5ex} {Moderate}& \raisebox{1.5ex} {High}\\
  
   \hline
  &&&\\
  \raisebox{1.5ex} {\textbf{Complexity }} & \raisebox{1.5ex} {Low} & \raisebox{1.5ex} {High}& \raisebox{1.5ex} {High}\\
  \hline
  
   
\end{tabular}
\caption{Comparsion of NFC, Bluetooth and WiFi }
\end{center}

\end{table}

  Compared to other short-range communication technologies, which have been integrated into mobile devices, NFC simplifies communication between mobile devices by establishing faster connections. 
             
\begin{itemize}
  \item \textit{NFC vs Bluetooth:} One of the significant advantage of NFC over Bluetooth is NFC requires shorter setup time.  The connection between two NFC devices can be estabilished by simply putting them in close proximity instead of manual configurations. 
  
  \item\textit{NFC vs WiFi:} Since the WiFi communication  is broadband internet access, it requires a hight complex infrasturcture with high power consumption. In addition to above mentioned complexity issues, NFC is more secure than WiFi since it's point-to-point rather than point-to-hub which is the case of WiFi.
  
\end{itemize}
   
    In addition, unlike Bluetooth and WiFi, NFC is compatible to RFID and consumes relatively lower energy. NFC also has an additional mode: acitve-passive mode.
  
\section{Problems and Solutions}
\subsection{Security Issues}
      NFC is ideal for transferring small packets of data between two devices that are in close proximity. The short transmission range makes NFC an inherently secure communication technology. However, the data itself in the transferring process is not encrypted, so it does not guarantee the security of the data transferring process. Nevertheless, secure data communication is necessary in many areas such as NFC mobile payment. Therefore, it is necessary to study the security techniques on NFC. 
 
     As a short range communication technique,  NFC involves conscious user interaction.  But this does not guarante it  will be secure, which has been studied and discussed in\cite{haselsteiner2006security},\cite{sarma2003rfid} and \cite{katz2010rfid} and give a very useful insight on that side. And also the vulnerability of RFID is also discussed on\cite{mitrokotsa2010classifying}. In this section, we will discuss several aspects of the security issues on NFC.
\subsubsection{Physical Attack} The communicating devices are liable to being manipulated physically; these attacks involve physical, mechanical, or chemical material that will hinder the NFC device(tag) from functioning  properly. The attacks which could be performed on the Tag are:
\begin{enumerate}
  \item \emph{Destruction}
This is the simplest attack which could be used and can compromise the availability of an NFC system. Such kind of attack could be done in different way. It could be mechanical, for example by cutting the connection to its antenna or an overpowered electrical field on the tags working frequency, so that the electrical components would overload. Destroying the electrical circuits of the tag could also be done by placing the tag into a microwave oven or exposing the device to some kind of chemical material.

\item \emph{Remove}
The tag could be removed from the carrier object. The motivation for this could be a thief, who wants to smuggle the carrier object through the security checks without recognition. 

\item \emph{ Shield}
 Placing the NFC device inside a metal box or a wrapping it in tinfoil could result a shielding attack which is only temporary, whereas destruction and removal attacks could lead to permanent loss of NFC from that device. This method could be used, for example, to pass automated toll checkpoints without recognition. 
 
 \item \emph{Clone}
Cloning attack is an attack which depends on the complexity of the tag being attacked, since the attacker needs to read the original tag and create an exact copy. If we take a read-only tag which stores only a simple numeric ID, it makes the cloning attack simple. Changing the ID over a defined period of time could be a nice solution.
 
 \item \emph{Falsify / Replace }
This attack overwrites the data of a tag or physically replaces it. Overwriting can be done easily if the original tag is a writeable tag without any security measures (or these measures are broken). The aim of this attack is to falsify the original tag, e.g. for phishing purposes.
\end{enumerate}

\subsubsection{Remote Attack}

 The technology can face the violation of privacy, i.e. there is copyrighted information stored on a tag in NFC device and it is important to prevent from unauthorized read and write access. Since the read-only tags does not allow the write access only the rewritable tags are susceptible to such kind of attacks. In these scenarios the assumption is that opponents are equipped with mobile readers and software that will allow them for an authorized read and write access. But there is always a consideration that the opponents’ reader device needs to be at a normal distance, since the NFC mechanism has a limit in the broadcast distance.
Cyclic redundancy check (CRC), a method that allows devices to check whether the received data has been corrupted, is used to detect whenever these kind of errors exits. But there are some threats which need a proper attention in the issue of NFC security and we will see different solutions have been provided in order to avoid or at least reduce these threats inflict.
\begin{enumerate}
\item\emph{Eavesdropping (Spying Out)}
NFC is a short range wireless communication, which makes it possible to suffer eavesdropping and this threat is an important issue. But this  issue is always doubted by many people asking a question:  how close the attacker needs to be in order to receive a usable RF signal. 
With the assumption of having an adversary with an antenna, the required knowledge on how to extract transmitted data out of the received RF signal and also equipped with an RF signal receiver and decoder, it is impossible to determine the proximity to the attacker needs in order be a potential threat to the parties using NFC. This is because there are several parameters that affect this issue, some of them related to the attacker’s behavior including the characteristics of the attacker’s antenna, quality of attacker’s receiver and RF signal decoder, and also setup of the location where the attacker is performed. And also behaviors of sender and sending device; RF field characteristic of the given sender device and power sent by the NFC device are influential on the issue mentioned above. In addition, the communication mode of the sender is also another very important feature, i.e., if sender is using the RF generated by another device(passive mode), which is harder to eavesdrop in comparison to sender generating its own RF field(active mode). 

Hence, the confidentiality of NFC is not guaranteed, as eavesdropping is a passive attack and it is difficult to for NFC parties to detect they are whether being spied or not, and with current technologies NFC device cannot protect against eavesdropping by itself. \cite{haselsteiner2006security} It is proposed that the only solution to this issue to establish a secure channel, if the applications are transmitting sensitive data.

\item\emph{Data Corruption/Destruction}
Most of the time an adversary aims not only for eavesdropping but also he intends to create confusion by corrupting the data that is being transmitted via NFC device. Even there is a possibility that the attacker to aspire data destruction, which results to total denial of service among the devices. Since this kind of attack is not passive, it is easy to realize especially in the case of total data destruction. 
In order to corrupt the data an attacker can transmit valid frequencies of the data spectrum at a correct time, if he/she has the ability to calculate it based on his high level understanding of the modulation scheme and coding. This kind of attack is explained in\cite{kerschbergernear} as RFI interface Jamming, a very simple but efficient method for interrupting data transmission. 
Though data corruption is not a complicated and also does not allow the attacker to manipulate the actual data, there is no way to prevent such an attack. But it is possible to detect it, since NFC devices are able to receive and transmit data at the same time, and they can do check in the RF field while transmitting data. If there is a data corruption a collision will be detected.

\item\emph{Data Modification}
In data modification,  the attacker wants the receiving device to actually receive some 
valid, but manipulated data. This is very different from just data corruption.  The feasibility of this attack highly depends on the applied strength of the amplitude 
modulation. This is because the decoding of the signal is different for differrent modulation.
   In order to prevent from being attacked by data modification, three different methods are proposed\cite{kerschbergernear}: Usage of the active communication mode with 106kbps. Though this would not prevent this attack, but it will at least reduce the risk.
Letting the devices check the RF field is also another way.
These above mentioned methods can provide some level of security but in order to achieve high level of data integrity, the best solution is using a secure channel.
\item\emph{Data Insertion}
This scenario exists when the attacker inserts messages into the data exchange process between two devices, but it’s not possible unless the answering device needs a very long time to answer. If a collision occurs the data exchange would be stopped at once. The adversary could then send his data earlier than the valid receiver. The insertion will be successful, only, if the inserted data can be transmitted, before the original device starts with the answer. If both data streams overlap, the data will be corrupted.
Data insertion can be avoided if the answering device is fast and gives answer without delay, this prevents insertion of data even if the attacker is as fast of that correct device. Other way of countermeasure for an attacker who wants to insert data is listening by the answering device to the channel during the time, checking the RF field. Creating a secure channel is a ultimate protection fo these attacks.

\item\emph{Man-in-the-Middle-Attack}
  Here two communicating parties make the assumption that they are having a private conversation, though there is a third party attacker who is part of their conversation.  This is a classical Man-in-the-Middle-Attack, the attacker tricking the NFC parties to have created a secure channel among each other which is quite difficult for the attacker to do. Because in order to do that, the attacker need to intercept the message sent from one device to another and prevent device B from receiving it. The next step would be replacing it with a different message.   Considering the NFC devices communication process, it will be possible for attackers to to eavesdrop and manipulate the transferring data, while both communicating NFC devices are assuming they are in a secure channel.
\end{enumerate}
\subsection{Other Challenges}
Security is the major issue with respect to NFC,  however, limited data transferring rates  and the availability of NFC-enabled devices are also challenging. 
\section{Future Trends}


As the mobile technology is gaining huge market share and is being deployed everywhere, the trend of NFC enabled moblies goes parallel with that. A report about the growth of NFC enabled mobile phones and their application is given in\cite{nfcmarket}, which clearly shows that companies are trying attaract customers by adding NFC technology to their mobile phones.

In 2011, only 5\% of the total mobile phones were NFC-enabled. It is estimated that in the coming five years, this number will rise to approximately 46\% by 2016. This indicates the rapid adoption of the NFC technology and the increasing mobile application of NFC technology. As more number of NFC products is made available, the market will see the growth in areas such as retail, ticketing, and smart advertisement application.

In that report the geographical distriution of NFC market is also explained in details, where it is almost evenly distributed amongst North America, Europe, and Asia-Pacific. North America and Europe are the major contributors in the NFC chips market with combined share of more than 60\%. Asia-Pacific is fast catching up and had almost one fourth of the share of the total chips market in 2011.

The growth of the NFC applications market is expected to be exponential with the revenue growth from \$7,686 million in 2011 to \$34,515 million by 2016, at an estimated CAGR of 35\% from 2011 to 2016. The most attractive of all the segments is the mobile payments segment; followed by the ticketing and access control. The major players that provide chips and controllers for the NFC products are NXP Semiconductors (U.S.), Broadcom (U.S.), and Renesas (Japan). 
\bibliography{citation}

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